Key entrapment lock device

ABSTRACT

A key entrapment lock device includes a cylinder plug having a keyway intersected by a passage making a wedging angle therewith. A ball in the passage is spring pressed to engage and wedge a key in the keyway when the key is moved in a withdrawing direction.

United States Patent Inventor Appl. No.

Filed Patented Assignee Ernest L. Schlage Burlingame, Calii. 815,832

Apr. 14, 1969 Apr. 13, 1971 Schlage Lock Company KEY ENTRAPMENT LOCKDEVICE 10 Claims, 9 Drawing Figs.

US. Cl 70/389, 70/386, 70/421 Int. Cl E05b 11/06 Field 01' Search 70/356,

References Cited UNITED STATES PATENTS 2/1912 Boone et al 1 l/ 1968Shiao-Ming l-lsu 1 H1969 Reisner FOREIGN PATENTS 3/1954 Germany PrimaryExaminerMarvin A. Champion Assistant Examiner-Robert L. WolfeAttorney-Lothrop and West Patented April '13, 1971 3,575,024

2 Sheets-Sheet 1 FIG- I VENTOR. Aw Jan/.44:

irrozvi'rs Patented April 13, 1971 3,575,024

2 Sheets-Sheet 2 F 9 INVENTOR.

im iir 4.501444:

KEY ENTRAPMENT LOCK DEVICE In many structures secured by lock deviceshaving pin tumbler mechanisms and actuated by keys it is possible forunauthorized persons to gain access to the space or object secured by alock device either by stealing the keys for the lock device or borrowingone or more keys temporarily and having additional keys made therefrom.This is particularly bothersome when the key misappropriated happens tobe a master key or a key having control over a main entrance to abuilding or control of several lock sets.

Recently it has become the custom of vandals to enter school buildings,for example, after misappropriating an access key or comparable key fromthe principals office and either utilizing it directly or having somecopies made. This may compromise the security of a large number of lockdevices. It is of course possible then to change all of the compromisedlock devices so that the previous keys are no longer effective. But thismay be an elaborate and expensive operation.

Much of the difficulty is due to vandals who are not professionals andare not intent on entering except by a fairly simple system, such as theone described. It has therefore occurred to me that a lock device, inaddition to being altered so that previously effective keys were stillreceived but were no longer effective, also could have the attribute ofcapturing or entrapping a previously effective key. In this instance itmight then be necessary to alter only one or two of the principal lockdevices in a system. Upon prompt recovery of the misappropriated keysthe rest of the system could safely be left as it was theretofore. As apractical example, a few'keycapturing lock devices were secretlyinstalled in a school complex. Within a 2-week period thereafter someseven unauthorized (previously effective) keys were retrieved. Retentionof the previously good keys by the undetected entrapment lock deviceswas unusual and was unexpected by the miscreants. The retention deviceswere also psychologically quite effective.

It is therefore an object of the invention to provide a lock devicehaving the ability to prevent the withdrawal of an unauthorized key.

Another object of the invention is to provide a lock device which notonly will entrap an unauthorized key but can be operated by anauthorized key.

Another object of the invention is to provide a key entrapping lockdevice which does not markedly differ in external appearance or apparentoperation from the normal lock device.

Another object of the invention is to provide a key entrapment lockdevice that, when knowledgeably handled, will readily release anentrapped key without the necessity of substantial disassembly or accessto the rear of the lock device.

Another object of the invention is to provide a key entrapment lockdevice that can readily be used with lock devices already existing.

Another object of the invention is in general to provide an improved keyentrapment lock device.

A further object of the invention is to provide a cylinder unit arrangedto trap or capture a key and to be substituted in a lock device for anormal cylinder unit.

Other objects together with the foregoing are attained in theembodiments of the invention described in the accompanying descriptionand illustrated in the accompanying drawings, in which:

FIG. I is an end view of a door panel on which a key entrapment lockdeviceis installed, certain portions being broken away to disclose theinterior configuration and reduce the size of the FIG.;

FIG. 2 is a cross section to an enlarged scale, the plane of sectionbeing indicated by the line 2-2 of FIG. 1;

FIG. 3 is a cross section, the planes of which are indicated by thelines 3-3 of FIG. 2;

FIG. 4 is an elevation of a releasing tool;

FIG. 5 is a cross section like FIG. 3 but showing an operable key inposition;

FIG. 6 is a cross section like FIG. 3 and showing a releasing tool inplace;

FIG. 7 is a view like FIG. 3 but showing a modification;

FIG. 8 is an elevation, portions being broken away, of a key foroperating the mechanism of FIG. 3; and

FIG. 9 is a cross section like a portion of FIG. 1 showing another formof operating key in position.

In one practical form the key entrapment lock device of the invention ismounted on a door panel 6 hinged to swing in the customary fashion. Thelock device includes a latch bolt 8 adapted to be projected from andretracted to the end face of the panel 6. The latch bolt 8 is connectedin the usual way for operation by a driver bar 9 extending along theaxis 11 of a spindle 12 mounted for rotation as part of the lock device.An actuating knob I3 is connected to the spindle and carries within it akey cylinder unit I4 of the usual sort. The cylinder body I5 of thecylinder unit has a tongue 16 within which the customary springs 17 andtumbler pins 18 are enclosed. Also included in the cylinder unit I4 is acylinder plug 19 rotatable about the axis Ill within the cylinder body15. It is the plug 19 that is directly connected to the driver bar 9 andis effective to produce retraction of the latch bolt 8.

The plug I9 in the customary fashion is pierced from endto-end to afforda keyway 21. This is an axially extending passageway having a number ofdifferent surfaces 22 on one side and 23 on the other to define atransverse cross section of any predetermined configuration. It iscustomary to have at least a part of the cross section, such as the wall24, of a generally planar character extending throughout all or most ofthe length of the keyway.

To facilitate the insertion of a key by axial movement toward thekeyway, the knob 13 is formed with a conical depression 26 leading tothe entrance to the keyway at the flanged end 27 of the plug. Thecooperating key 28 has a bow 20 merging with a shank 3I conforming incross section to the configuration of the keyway 21. Along one edge 32the shank has a number of serrations to correspond with the tumbler pins18. The key customarily is long enough and is so contoured as to actuateall of the five or more tumbler pins 18 arranged in line within thecylinder tongue I6.

In the normal use of the structure, the key 28 is inserted fully intothe keyway, thus positioning all of the tumblers 18 so that a uniformshear line exists between the plug 19 and the cylinder body 15. Afollowing rotation of the key produces rotation of the plug and likewiseof the driver bar 9. This releases the latch bolt 8 and permits swingingof the door panel 6. Following the unlocking operation the key isrotated to initial position and can be withdrawn in an axial direction.The tumblers I3 under influence of the springs 17 return to theirpositions across the shear line between the rotatable plug and thecylinder.

Pursuant to the present invention, the entrapment cylinder plug ispreferably provided, as particularly shown in FIGS. 2 and 3, with apassage 36 generally circular cylindrical in character arrangedapproximately at the level of the flat wall 24 and having its own axis37 intersecting the axis 11 of the rotatable plug at a relatively smallangle a; for example, about 8". This angle is referred to as a wedgingangle to distinguish between a small angle of this sort at which awedging operation can readily occur and a larger angle at which nowedging occurs. The difference between the small wedging angle and alarger nonwedging angle is, in many instances, only a relatively fewdegrees. In the present instance, the axis 37 is not parallel to theaxis II in side elevation. The actual angle between the axes is thus notexactly the angle measured in plan. The difference is slight and notmaterial.

Disposed in the passage 36 is a jamming or wedging body 38 preferably aball, such as a bearing ball. Behind the ball there is located a helicalspring 39. At one end the spring abuts the ball and at the other endcarries a cap 41 serving as a seat and stop for the spring. The capabuts the end of the driver bar 9. The spring 39 urges the ball towardand even part way into the keyway 21. The ball is large enough whenstopped against the end of the passage 36 to emerge slightly into thekeyway.

With this mechanism, a regular key 28 can be introduced by axialmovement into the keyway 21 without any apparent difference to the user.In entering the keyway, the key first displaces the projecting ballfarther into the intersecting passage 36. However, the spring pressureon the ball continually urges the ball into immediate contact with theflat surface of the key. In an instance in which the lock device isinstalled overhead with the axis ll vertical, the spring may not beneeded, gravity being sufficient to hold the ball into contact with thekey. Prior to the substitution of the present entrapment cylinder unit14 in the lock device, the earlier cylinder unit cooperated fully withthe key 28 to rotate the driver bar 9. The entrapment cylinder unit I4,although having a keyway cross section capable of receiving the key 28,has a different arrangement of the pins I8 and so no plug or driver barrotation is possible. The key can be inserted but not turned and socannot unlock the lock device. The frictional engagement between the keyand the ball is sufiicient so that, when the user attempts to withdrawthe key by a retracting movement along the axis 11, the ball wedgesbetween the wall of the passage 36 and the key. In fact, the withdrawalmotion, though minute, tends to displace the key laterally in adirection away from the passage 36. The wedging engagement is sufficientso that the key cannot be withdrawn.

There are various ways of removing the key from its entrapped orcaptured condition or position.

One way is to release the door panel 6 from the interior, then dismantlethe entire lock device to gain access to the cylinder unit. Disassemblyof the cylinder unit permits removal of the spring and ball from theplug interior. The key can then be withdrawn. This, however, is a timeconsuming and may be an expensive proceeding. Instead I prefer slightlyto enlarge, if necessary, the transverse dimension of the keyway and toprovide a piece of shim stock 44 (FIG. 4) of a thickness just sufficientto be insertable into the space alongside the key 28 in the keyway 21(FIG. 6) when the key is moved sideways under the influence of the ballor any lateral force. A person having knowledge of the mechanism caninsert the piece of shim stock 44 from the entrance end of the keywayalongside the flat portion thereof and by engaging the ball from theentrance end can displace the ball inwardly and correspondingly somewhattransversely, thereupon compressing the spring slightly and releasingthe ball from the key. The key can then be withdrawn from the front.

A variation on this arrangement is afforded by a special bore 46 in theplug (FIG. 7) opening into the passage 36 and emerging alongside thekeyway at the plug surface. A wire 47 can be introduced from the frontto dislodge and release the ball and so to free the key. This variationavoids any necessity of partially enlarging the keyway to receive thepiece'of shim stock 44, but does make a visible change in the looks ofthe front of the plug and so may mark its unique character.

As an expedient for those authorized, there can be provided to actuatethis particular lock device a special key 48 as shown in FIG. 5. In thisinstance the key, in all parts which might be contacted by the ball, hasa taper portion 49 so that the resulting angle b between the surface 49of the key and the axis of the ball passage 36 is greater than thewedging angle. This tapered key, although generally in appearance notnotably distinguished from the previously effective key, will not becaptured since the angle is too great for the ball and key blank towedge. As another expedient, the bottom portion of an authorized key 51can be cut away (FIG. 8) so that it has no part in position to beengaged by the ball although it can actuate all the tumbler pins 18.Furthermore, a short key 52 (FIG. 9) can be provided to stay out of thepath of the ball if various of the inner tumbler pins I8 are omitted.

With an entrapment lock device of this sort it is possible to provide anew system of security simply by changing one or two of the most likelylock devices. These can still be actuated, despite changes in their pintumbler setup, by special keys known to those authorized, yet areeffective to capture previously effective keys and prevent their furtheruse.

Iclaim:

I. A key entrapment lock device comprising a cylinder plug having anaxis, means in said plug defining a keyway having a first wall extendingparallel to said axis, means in said plug defining a passage having asecond wall intersecting said first wall at a wedging angle to saidaxis, and a body in said passage movable into and away from a positionin said passage in which said body is wedged between said first wall anda key wall on a key in said passage and disposed substantially parallelto said first wall. I

2. A key entrapment lock device as in claim 1 including a spring in saidpassage urging said body toward said keyway.

3. A key entrapment lock device as in claim 1 in which said body is aball.

4. A key entrapment lock device as in claim I in which said keywayextends into said plug a predetermined distance and said passageintersects said keyway at a point about midway of said distance.

5. A key entrapment lock device as in claim I in which said keyway isproportioned with respect to said key to leave an access channel betweensaid key and said plug from the entrance end of said plug to said body.

6. A key entrapment lock device as in claim 5 in which said accesschannel and said body are on the same side of said keyway.

7. A key entrapment device as in claim 1 in combination with a keyhaving a surface which when said key is in said keyway abuts said bodyat an angle less than a wedging angle between said key surface and saidbody.

8. A key entrapment device as in claim I in combination with a keyhaving a surface which when said key is in said keyway abuts said bodyat an angle greater than a wedging angle between said key surface andsaid body.

9. A key entrapment device as in claim 1 in combination with a keyhaving a surface which when said key is in said keyway is spaced awayfrom said body but if continued would abut said body at a wedging angle.

I0. A key entrapment device as in claim 1 including means defining abore in said plug extending from the exterior thereof substantially tosaid passage.

1. A key entrapment lock device comprising a cylinder plug having anaxis, means in said plug defining a keyway having a first wall extendingparallel to said axis, means in said plug defining a passage having asecond wall intersecting said first wall at a wedging angle to saidaxis, and a body in said passage movable into and away from a positionin said passage in which said body is wedged between said first wall anda key wall on a key in said passage and disposed substantially parallelto said first wall.
 2. A key entrapment lock device as in claim 1including a spring in said passage urging said body toward said keyway.3. A key entrapment lock device as in claim 1 in which said body is aball.
 4. A key entrapment lock device as in claim 1 in which said keywayextends into said plug a predetermined distance and said passageintersects said keyway at a point about midway of said distance.
 5. Akey entrapment lock device as in claim 1 in which said keyway isproportioned with respect to said key to leave an access channel betweensaid key and said plug from the entrance end of said plug to said body.6. A key entrapment lock device as in claim 5 in which said accesschannel and said body are on the same side of said keyway.
 7. A keyentrapment device as in claim 1 in combination with a key having asurface which when said key is in said keyway abuts said body at anangle less than a wedging angle between said key surface and said body.8. A key entrapment device as in claim 1 in combination with a keyhaving a surface which when said key is in said keyway abuts said bodyat an angle greater than a wedging angle between said key surface andsaid body.
 9. A key entrapment device as in claim 1 in combination witha key having a surface which when said key is in said keyway is spacedaway from said body but if continued would abut said body at a wedgingangle.
 10. A key entrapment device as in claim 1 including meansdefining a bore in said plug extending from the exterior thereofsubstantially to said passage.